Silicon-silicon oxide-lithium composite material having nano silicon particles embedded in a silicon:silicon lithium silicate composite matrix, and a process for manufacture thereof

ABSTRACT

A process for producing a silicon:silicon oxide: lithium composite (SSLC) material useful as a negative electrode active material for non-aqueous battery cells includes: producing a partially lithiated SSLC material by way of mechanical mixing; subsequently producing a further prelithiated SSLC material by way of spontaneous lithiation procedure; and subsequently producing a delithiated SSLC material by way of reacting lithium silicide within the dispersed prelithiated SSLC material with organic solvent(s) to extract lithium from the prelithiated SSLC material, until reactivity of lithium silicide within the prelithiated SSLC material with the organic solvent(s) ceases. The delithiated SSLC material is a porous plastically deformable matrix having nano silicon embedded therein. The delithiated SSLC material can have a lithium silicide content of less than 0.5% by weight. A battery cell having as its negative electrode active material an SSLC material as set forth herein can exhibit an irreversible capacity loss of less than 10%.

TECHNICAL FIELD

Aspects of the present disclosure relate to a silicon-siliconoxide-lithium silicate composite (SSLC) based material having nanosilicon particles embedded in a silicon:lithium silicate composite(Si:LSC) matrix, and a process for preparing the same. The SSLC basedmaterial is useful as a negative electrode active material (where anegative electrode conventionally corresponds to a negative terminal ofa battery or battery cell during battery discharge) for non-aqueouselectrolyte battery cells, such as lithium ion battery cells.

BACKGROUND

The rapid development and market growth of mobile devices and electricvehicles has resulted in strong demand for low cost, small size,lightweight, high energy density secondary batteries, such as lithiumion batteries. In the development of high energy density secondarybatteries, cathode material technology is a well-recognized bottleneck,because cathode materials exhibit a lower capacity than anode materials.However cathode materials capacity improvement has been incremental,while anode capacity improvement can be improved many times by movingfrom conventional graphite to none carbon based anode materials.Consequently, there have been extensive development efforts to producehigh capacity anode materials, because a higher capacity anode cansignificantly increase the energy density of a commercial secondarybattery, for instance, by up to 25%, when the battery is fabricatedusing a given type of commercially available cathode materialtechnology.

Silicon (Si) has been investigated as an anode material for lithium ion(Li⁺) batteries because it exhibits a high theoretical capacity (e.g.,up to 3750-4200 mAh/g) as a battery cell anode material, and is anabundant, inexpensive element that is readily available as a result ofits widespread use in the semiconductor industry. The electrochemicallithiation and delithiation of silicon can be generally represented asxLi⁺+Si+xe ⁻

Li_(x)Si  (1)

With respect to the use of silicon as an anode material, this hightheoretical capacity results in a significant theoretical increase inthe energy density and specific energy of the cell compared to graphiteanode materials.

Pure silicon anodes show excellent cyclic performance when a nano thinSi film is coated on conducting graphite/carbon, or when nano sized Siis composited with nano featured metal current collectors. Silicon nanowire and silicon nano particles also show good cyclic performancedepending on the properties of various polymeric binders used therewith.However, these nano structured silicon anodes work well only at very lowloading density. To increase the energy density of the battery cell, theloading density of the anode is increased. This means the anode isimpregnated with a higher ratio of active material weight to inactivecomponents in lithium ion cells. However, as the loading densityincreases, the electrodes collapse after initial cycles and the cyclicperformance deteriorates.

Unfortunately, silicon anodes also exhibit a large first-cycle capacityloss, side reactions during cycling, and a very large volume changeduring battery cell charge-discharge or lithiation-delithiation cycles(e.g., up to 300-400%). With respect to this volume change, duringlithium ion battery cycling, the Si anode is lithiated by intercalation(i.e., reversible insertion) of 4.4 Li atoms per Si atom. The very largevolume change leads to mechanical failure and capacity fading.

Silicon oxide (SiO_(x)) has also been investigated for use as an anodematerial for lithium ion batteries, particularly because this materialshows much less volume change after the first cycle compared to puresilicon anode materials. SiO_(x) is regarded as a uniform mixture ofnano sized Si and SiO₂ phases that form upon energetic treatment oforiginal SiO_(x) material, as described by K. Schulmeister and W. Maderin “TEM investigation on the structure of amporphous silicon monoxide,”Journal of Non-Crystalline Solids 320 (2003), pp. 143-150. When themolar ratio of Si to SiO₂ is 1, its volumetric ratio is 0.5. Thisindicates that nano silicon particles are embedded in a matrix of SiO₂in the SiO_(x) material structure.

The electrical conductivity of SiO_(x) is low, and as SiO_(x) islithiated its electrical conductivity decreases. This poor electricalconductivity contributes to decreases in utilization of SiO_(x) duringcycling. The electrical conductivity of SiO_(x) can be improved bymechanically milling SiO_(x) (0.8<x<1.5) with graphite using high energymechanical milling, as described in U.S. Pat. No. 6,638,662; or coatingSiO_(x) particles with a uniform carbon layer using thermal ChemicalVapor Deposition (CVD), as described in Japanese patent publication JP-A2002-042806. These techniques successfully increase charge-dischargecapacity, but fail to provide sufficient cyclic performance, and thus donot meet the market requirements for high energy density batteries.Therefore, such techniques have not been successfully utilized toproduce commercial products in the market, as further improvement incycle performance is imperative.

Another problematic electrochemical property of SiO_(x) based anodes isa high irreversible capacity loss on the first charge/discharge cyclebelow a practical level, as described in U.S. Pat. No. 5,395,811. Asindicated in U.S. Pat. No. 7,776,473, the irreversible capacity loss ofSiO_(x) anode material can be reduced by way of prelithiating theSiO_(x) material.

U.S. Pat. Nos. 7,776,473 and 8,231,810 respectively indicate thefollowing reactions between lithium and SiO:4Li+4SiO→Li₄SiO₄+3Si  (2)4Li+4SiO→3Si:Li₄SiO₄  (3)

The chemical reaction mainly forms lithium silicate (Li₄SiO₄) andsilicon. In view of the aforementioned mixture of nano sized Si and SiO₂within SiO_(x), the reaction between lithium and SiO_(x) can beexpressed as follows:4Li+2SiO₂→Li₄SiO₄+Si→Si:Li₄SiO₄(Si:LSC)  (4)

Depending on reaction conditions, some research groups have indicatedthat lithium silicate consists of Li₄SiO₄, Li₂O, and Li₂SiO₃. The majorcomponent may be Li₄SiO₄. The irreversible chemical reaction of Li andthe SiO₂ matrix in the SiO_(x) structure also forms a certain amount oflithium silicide (Li_(y)Si).

During the first lithiation of SiO, when the SiO₂ phase irreversiblychanges into the mixture of Li₄SiO₄ and Li_(y)Si, the volume increasesby a factor of two. During delithiation, Li₄SiO₄ remains Li₄SiO₄, andLi_(y)Si becomes silicon. As a result, Si:LSC (Si:Li₄SiO₄) becomesporous, and because of plastic deformation of Li₄SiO₄, the volume changefrom Li_(y)Si:Li₄SiO₄ to Si:Li₄SiO₄ can be minimized. Consequently, thevolume change of SiO_(x) based anode particles is much smaller than thatof pure silicon anode particles after the first cycle. Additionally,SiO_(x) based anodes generally show much better cyclic performancecompared with pure Si based anodes after the first cycle, under thecondition that both are micro-sized.

U.S. Pat. No. 7,776,472 teaches the prelithiation of SiO_(x) by millingSiO_(x) powder with active lithium powder through a high energy ballmilling process. This prelithiation successfully reduces theirreversible capacity loss from 35% to 15%. However, U.S. Pat. No.7,776,472 also indicates that as a result of this prelithiation process,the reversible capacity was only 800 to 900 mAh/g, whereas most SiO_(x)anodes coated with graphite show a reversible capacity of 1400 to 1700mAh/g. Unfortunately, the results obtained by the process of U.S. Pat.No. 7,776,472 are not sufficient for satisfying the characteristicsrequired for a commercial anode material. Lower irreversible capacityloss of the first cycle and improved cyclic performance are stillrequired.

Further to the foregoing, while anode material prelithiation can reduceirreversible capacity loss, prelithiated anode materials have anundesirably high chemical reactivity due to the presence of highlyreactive, chemically unstable lithium therein. This high chemicalreactivity can lead to difficulties in handling and processingprelithiated anode materials during conventional battery manufacturingprocesses, or render the prelithiated anode materials incompatible withconventional battery manufacturing processes. For instance, prelithiatedanode materials may be incompatible with solvents, binders, thermalprocessing conditions, and/or ambient environments commonly encounteredin battery manufacturing processes. A need also exists to overcome thisproblem.

DISCLOSURE

In the present disclosure, depiction of a given element or considerationor use of a particular element number in a particular FIG. or areference thereto in corresponding descriptive material can encompassthe same, an equivalent, or an analogous element or element numberidentified in another FIG. or descriptive material associated therewith.The use of “/” in a FIG. or associated text is understood to mean“and/or” unless otherwise indicated. The recitation of a particularnumerical value or value range herein is understood to include or be arecitation of an approximate numerical value or value range, forinstance, to within +/− 10%, +/− 5%, +/− 2.5%, or +/− 1% of a particularnumerical value or value range under consideration.

Further Aspects of the Technical Problem

As indicated above, high capacity silicon oxide based anodes offerexcellent cyclic performance at higher loading density compared to puresilicon based anodes, but silicon oxide based anodes suffer from lowinitial efficiency. Although irreversible capacity loss can be reducedin the manner disclosed by U.S. Pat. No. 7,776,473, the inventors of thepresent application have found that prelithiation in accordance with theteachings of U.S. Pat. No. 7,776,473, which is performed by ball millingsolid state materials (i.e., solid silicon oxide powder and metalliclithium powder), results in incomplete and non-uniform lithiation. Thatis, complete, uniform prelithiation of SiO_(x) by ball milling solidstate materials in the manner disclosed by U.S. Pat. No. 7,776,473 isdifficult to achieve.

U.S. Pat. No. 7,776,473 discloses that the rate of diffusion of metalliclithium into solid SiO_(x) is low, making it difficult for metalliclithium to uniformly penetrate into the SiO_(x). Furthermore, the use oflarger amounts of metallic lithium powder during ball milling topotentially provide a greater concentration of lithium available fordiffusion into SiO_(x) is not feasible in view of safety concerns due tothe highly reactive nature of lithium, as well as the need to removedecomposed products during the ball milling process. U.S. Pat. No.7,776,473 teaches the use of a small, controlled amount of lithiumpowder, such that the amount of lithium added provides an atomic ratioof lithium to oxygen less than or equal to 2 (i.e., Li/O<2). U.S.7,776,473 further teaches that after the reaction of SiO_(x) withmetallic lithium through ball milling, an organolithium compound (e.g.,alkyllithium or aryllithium) can be added to compensate for orcomplement a lithium shortage. Notwithstanding, even with such additionof an organolithium compound (butyllithium), the prelithiation processtaught by U.S. Pat. No. 7,776,473 results in a commercially unacceptablelow reversible capacity of 800-900 mAh/g, in contrast to conventionalcarbon coated SiO_(x) anodes that exhibit a reversible capacity of1400-1700 mAh/g.

The prelithiation process disclosed in U.S. Pat. No. 7,776,473 cannotavoid the formation of lithium silicide. The low reversible capacity of800-900 mAh/g obtained by the process of U.S. Pat. No. 7,776,473indicates that after this process is performed, lithium silicide remainsat the surface of the particles produced, and may be oxidized when theparticles are exposed to air, thus reducing conductivity. Additionally,lithium silicide that remains on the surface of the particles will causethe gellation of an electrode slurry mixture by reacting with polymerbinders or N-methyl-pyrolidone (NMP).

As also indicated above, prelithiated anode materials have anundesirably high chemical reactivity due to the lithium containedtherein, which can lead to handling difficulties or incompatibilityissues when prelithiated anode materials are used in conventionalbattery manufacturing processes.

Technical Solution and Summary

Embodiments in accordance with the present disclosure are directed to afully delithiated silicon-silicon oxide-lithium composite (SSLC)particulate material or SSLC based particulate material having amorphousand/or crystalline nano silicon particles embedded in a porous,plastically deformable silicon:lithium silicate composite (Si:LSC)matrix. In various embodiments, this SSLC/SSLC based material has anaverage particle size of approximately 1 to 10 μm; the Si:LSC matrix hasparticle or grain sizes of 10-200 nm; and the nano silicon particlesembedded therein have particle or grain sizes of approximately 0.5-150nm (e.g., 0.5-80 nm, or 0.5-50 nm).

Embodiments in accordance with the present disclosure arecorrespondingly directed to a process for producing or manufacturing anSSLC/SSLC based material, where the process includes a first processportion involving complete or essentially complete and uniformprelithiation of SiO_(x) and the production of the SSLC/SSLC basedmaterial having lithium silicide uniformly distributed therein; followeda second process portion involving complete or essentially completedelithiation of the SSLC/SSLC based material. The delithiated SSLC/SSLCbased material is suitable for use in battery manufacturing processes(e.g., conventional battery manufacturing processes) as a result oflacking lithium therein. Embodiments in accordance with the presentdisclosure are further directed to use of a delithiated SSLC/SSLC basedmaterial in the production or manufacture of a battery cell or battery;and also to a battery cell anode made with the delithiated SSLC/SSLCbased material.

Such a SSLC/SSLC based material when used as negative electrode activematerial for non-aqueous electrolyte battery cells, such as lithium ionbattery cells, has many advantages. The porous, already plasticallydeformable Si:LSC matrix greatly reduces or minimizes any volume changesassociated with lithiation/delithiation of the SSLC/SSLC based materialduring the charge and discharge process. When used as negative electrodeactive material in a lithium ion battery cell, an SSLC/SSLC basedmaterial in accordance with an embodiment of the present disclosure canexhibit a volume change of approximately 7-35% (e.g., averagingapproximately 15-35%, or approximately 10-20%) between lithiation(charging) and delithiation (discharging). This compares very favorablyto earlier use of Si in SiO₂ as anode where during lithiation anodeundergoes an unacceptably large volumetric change, e.g., of up to 200%.

In view of the foregoing, when essentially fully or fully prelithiatedSSLC/SSLC based material is produced in accordance with an embodiment ofthe present disclosure, such prelithiated SSLC/SSLC based material willexhibit or occupy a maximized, essentially maximum, or maximum volume(or correspondingly, a maximum extent of volumetric expansion). Whenthis essentially fully or fully prelithated SSLC/SSLC based material isthen essentially fully or fully delithiated (which occurs prior to itsuse in a lithium ion battery, battery cell, or anode manufacturingprocess), it will exhibit or occupy a minimized, essentially minimum, orminimum volume (or correspondingly, a maximum extent of volumetriccontraction). When such essentially fully or fully delithiated SSLC/SSLCbased material is subsequently used as an anode active material in abattery cell, in association with battery cell (re)charging anddischarging by way of anode active material lithiation and delithiation,respectively, the volume change of the SSLC/SSLC based anode activematerial will approximately range or transition between theaforementioned volumetric extremes, e.g., the maximum volume of theprelithiated SSLC/SSLC based material and the minimum volume of thedelithiated SSLC/SSLC based material.

Because the maximum extent of volumetric change, transition, shift, orswing of the SSLC/SSLC based active anode material in a lithium ionbattery cell is limited to 10-35% rather than a much or dramaticallylarger volumetric change such as 200%, this means that either (a) for agiven, target, or predetermined size anode, the use of the SSLC/SSLCbased material in battery cell manufacturing can result in a batterycell having a significantly or much greater energy density/capacity; or(b) a significantly or much smaller amount of SSLC/SSLC based materialcan be used in a battery cell manufacturing process to produce an anodefor a given energy density/capacity, resulting in a much smaller orthinner anode and hence a significantly or much smaller or thinnerbattery cell with higher energy density/capacity. For instance, anSSLC/SSLC based material in accordance with an embodiment of the presentdisclosure can exhibit an energy density that is approximately 300%greater than that of a conventional graphite material. Therefore, theuse of an SSLC/SSLC based material as an anode active material in alithium ion battery cell means that (i) for a battery cell anode of agiven, target, or predetermined size, the battery cell can have acapacity that is roughly or approximately 300% greater than a batterycell that uses conventional graphite material as its active anodematerial; or (ii) for a battery cell of a given, target, orpredetermined capacity, the size of the battery cell anode can beroughly or approximately ⅓ that of a battery cell anode that usesconventional graphite material as its active anode material.

Further to the foregoing, individuals having ordinary skill in therelevant art will recognize that the extent or range of the batterycell's overall volumetric change as a result of (re)charging anddischarging will be less than the extent of volumetric change of thebattery cell's anode. More particularly, the overall extent of thebattery cell's volumetric change depends upon the thickness of thebattery cell's anode relative to the thickness of the battery cell'scathode; and the anode is commonly or typically significantly or muchthinner than the cathode (e.g., the anode may only be approximately ⅓ asthick as the cathode). Moreover, cathode active materials commonlyexhibit a smaller or much smaller change in volume in association withbattery cell (re)charging and discharging. Consequently, the overallextent of volume change or volumetric expansion and contraction of abattery cell that uses as its active anode material an SSLC/SSLC basedmaterial in accordance with an embodiment of the present disclosure canbe approximately 3-10% (e.g., approximately 5%-8%).

Additionally, a lithium ion battery cell that includes an SSLC/SSLCbased anode material in accordance with an embodiment of the presentdisclosure can exhibit a reversible capacity loss of less than 15%(e.g., less than 12%, or less than 10%, or within a range ofapproximately 8%-12%), which is a significant reduction in irreversiblecapacity loss compared to the prior art, and which meets commercialrequirements.

Moreover, such a lithium ion battery cell can exhibit a reversiblecapacity of greater than approximately 1100 mAh/g (e.g., 1200 mAh/g orhigher). Lastly, to facilitate its use in an anode or anode cellmanufacturing process, the SSLC/SSLC based material is delithiated priorto its use in the manufacturing process, and will not contain activelithium therein (i.e., the SSLC/SSLC based material would have beendelithiated, such that the lithium from the active lithium silicidewould have been removed from the final as-produced SSLC/SSLC basedmaterial), and hence does not give rise to battery manufacturing processrelated handling or incompatibility issues.

In the disclosure herein, an SSLC based material can be defined as anSSLC material in which SiO_(x) has been conductivity-enhanced prior toor in association with prelithiation. For instance, an SSLC basedmaterial can be a silicon-silicon oxide-lithium-carbon orsilicon-silicon oxide-lithium-carbon based composite (SSLCC) material,in which the electrical conductivity of SiO_(x) has been enhanced by wayof treating or combining the SiO_(x) with a carbon based material suchas graphite prior to or in association with prelithiation, as furtherdetailed below. For purpose of brevity and simplicity, in thedescription that follows, the term “SSLC material” encompasses orincludes an SSLC based material such as an SSLCC material.

In accordance with an aspect of the present disclosure, a process forproducing a silicon:silicon oxide: lithium composite (SSLC) materialincludes peforming a prelithiation process and a delithiation process.The prelithiation process results in the production of a prelithiatedmaterial, and includes producing a partially lithiated SSLC material byway of a mechanical mixing procedure comprising milling silicon oxidepowder and lithium powder; and producing a further prelithiated SSLCmaterial by way of a spontaneous lithiation procedure including:compressing the partially lithiated SSLC material matrix material; andexposing the compressed partially lithiated SSLC material to an lithiumbased electrolyte, wherein spontaneous lithiation procedure completesreaction of unreacted lithium and SiO_(x) in the partially lithiatedSSLC material, until unreacted lithium disappears and a uniformcomposition of lithium silicides is achieved in the SSLC material bylithium diffusion. The delithiation process follows the prelithinationprocess and results in the production of a delithiated SSLC material.The delithiation process includes dispersing the compressed furtherprelithiated SSLC material in a liquid carrier medium to thereby producea dispersed prelithiated SSLC material; and exposing the dispersedprelithiated SSLC material to a volume of one or more organic solventsto thereby react lithium silicide within the dispersed prelithiated SSLCmaterial with the one or more organic solvents and extract lithium fromthe dispersed prelithiated SSLC material, until reactivity of lithiumsilicide within the dispersed prelithiated SSLC material with the one ormore organic solvents ceases, wherein the volume of the one or moreorganic solvents acts as a reservoir with respect to reacting withlithium silicide within the dispersed prelithiated SSLC material,wherein the delithiated SSLC material comprises a porous plasticallydeformable Si:lithium silicate composite (Si:LSC) matrix having nanosilicon particles embedded therein.

The delithiated SSLC material can have a lithium silicide content ofless than 0.5% by weight. The delithiated SSLC material can have aparticle size of 1 to 10 μm, the Si:LSC matrix can exhibit a grain sizeof 10-200 nm, and the nano silicon particles can have a particle size of5-150 nm (e.g., 5-80 nm, or 5-50 nm). In various embodiments, thedelithiated SSLC material has a silicon content of 30%-60% by weight, anoxygen content of 25%-40% by weight, and a lithium content of 10%-20% byweight. The delithiated SSLC material can have a composition ofapproximately 37% silicon by weight, approximately 18% lithium byweight, and approximately 43% oxygen by weight.

The liquid carrier medium includes an aprotic solvent, and the one ormore organic solvents includes an alcohol. For instance, the liquidcarrier medium can include hexane, and the one or more organic solventscan include ethanol, glycerol, and/or polyvinyl alcohol (PVA).

The silicon oxide powder can be characterized as SiOx (0.8<x<1.6), andthe mechanical mixing procedure can include ball milling the siliconoxide powder with the lithium powder, and the lithium powder can includeor be SLMP®.

The process can include performing a first electrical conductivityenhancement process prior to the prelithiation process, wherein thefirst electrical conductivity enhancement process comprises least one ofball milling the silicon oxide powder with a carbon based material, andcoating the silicon oxide powder with a carbon based material.Additionally or alternatively, the process can include performing asecond electrical conductivity enhancement process after thedelithiation process, wherein the second electrical conductivityenhancement process comprises at least one of ball milling the siliconoxide powder with a carbon based material, and coating the silicon oxidepowder with a carbon based material. The carbon based material caninclude at least one of graphite, carbon black, buckyballs, carbonnanotubes, carbon megatubes, and carbon nanobuds.

In accordance with an aspect of the present disclosure, a delithiatedSSLC material is produced by the process set forth above and has alithium silicide content of less than 0.5% by weight.

In accordance with an aspect of the present disclosure, a delithiatedSSLC material that is produced by the process set forth above and whichhas a lithium silicide content of less than 0.5% by weight is used in abattery cell negative electrode manufacturing process.

In accordance with an aspect of the present disclosure, a lithium ionbattery cell has as its negative electrode active material an SSLCmaterial, and exhibits an irreversible capacity loss of less than 15%(e.g., less than 12%, or less than 10%). The SSLC active material can beproduced by the process set forth above. An anode of the lithium ionbattery cell can exhibit a volume change of 10-35% (e.g., an averagevolume change of 15-25%, or an average volume change of 20%) inassociation with lithium ion battery cell charging and discharging.

Particular Advantageous Effects

An SSLC material production process in accordance with an embodiment ofthe present disclosure provides a simple, robust, commercially scalable,cost effective process by which an SSLC material useful as a negativeelectrode material that satisfies market requirements can be produced.The SSLC material can be used as a negative electrode material toproduce a lithium ion battery anode that exhibits more uniform oruniform and greatly reduced or minimal, volume change as a result oflithiation and delithiation, and which has an irreversible capacity lossthat is significantly or greatly reduced compared to prior SiO_(x) basedanodes. To facilitate its use in battery manufacturing processes, theSSLC material is completely delithiated, and thus the SSLC material iscompatible with solvents, binders, thermal processing conditions, and/orambient environments associated with typical battery manufacturingprocesses. In addition, an electrode slurry containing an SSLC materialproduced in accordance with an embodiment of the present disclosureforms a good laminated electrode structure without forming a deleteriousgel, even when a relatively large amount of lithium has been used toprelithiate SiO_(x) particles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of a representative process for producing ormanufacturing a silicon-silicon oxide-lithium composite (SSLC) materialstructure, or composition in accordance with an embodiment of thepresent disclosure.

FIG. 2 is a schematic illustration of a representative delithiationreactor in accordance with an embodiment of the present disclosure.

FIGS. 3A-3C are illustrations of representative microstructuralcharacteristics of SiOx (x=1); representative microstructuralcharacteristics of prelithiated SSLC produced in accordance with anembodiment of the present disclosure; and representative microstructuralcharacteristics of delithiated SSLC produced in accordance with anembodiment of the present disclosure, respectively.

DETAILED DESCRIPTION OF REPRESENTATIVE EXAMPLE EMBODIMENTS

Overview of a Representative SSLC Material Production Process

FIG. 1 is a flow diagram of a representative process 100 for producingor manufacturing an SSLC material, material structure, or composition inaccordance with an embodiment of the present disclosure. In variousrepresentative embodiments, the SSLC material production process 100includes a first process portion 110 by which prelithiated SSLC materialis produced; a second process portion 120 by which this prelithiatedSSLC material is delithiated; a third process portion 130 by which thedelithiated SSLC material is filtered, washed, and dried; possibly afourth process portion 140 by which the delithiated SSLC material iscoated with one or more materials for purpose of enhancing mechanical orstructural integrity or stability; and typically a fifth process portion150 by which the delithated SSLC material or the mechanically stabilizedSSLC material is coated or combined with carbon or a carbon basedmaterial to enhance electrical conductivity. Aspects of the SSLCmaterial production process 100 are described in detail hereafter.

The first process portion 110 produces the prelithiated SSLC material byway of a first or initial prelithiation procedure 112, followed by asecond or subsequent prelithiation procedure 114. The firstprelithiation procedure 112 produces a partially lithiated SSLCmaterial, after which the second prelithiation procedure 114 produces anSSLC material that exhibits a significantly enhanced, substantiallycomplete, or complete extent of lithiation compared to the prior art.More particularly, in the first prelithiation procedure, SiO_(x) and/orconductivity-enhanced SiO_(x) in powder form can be mixed, combined,and/or reacted with metallic lithium, such as stabilized lithium powder(e.g., SLMP® from FMC Corporation, Charlotte, N.C. USA,www.fmclithium.com), to produce the partially lithiated SSLC material inpowder form. The first or initial prelithiation procedure 112 can besimilar, generally analogous, analogous, substantially identical,essentially identical, or identical to that disclosed in U.S. Pat. No.7,776,473, which is incorporated herein by reference.Conductivity-enhanced SiO_(x) can be produced for use in or as part ofthe first prelithiation procedure 112 by way of treating, coating, orcombining SiO_(x) with one or more carbon or carbon based material suchas graphite, carbon black, graphene, buckyballs, carbon nanotubes,carbon megatubes, and/or carbon nanobuds in a conventional manner, aswill be readily understood by individuals having ordinary skill in therelevant art. In some embodiments, conductivity-enhanced SiO_(x) isproduced by ball milling SiO_(x) with one or more carbon or carbon basedmaterials, which can result in carbon or carbon based particles enteringor becoming part of agglomerated SiO_(x) particles produced during ballmilling. Such ball milling can occur by way of a procedure that issimilar, generally analogous, analogous, substantially identical,essentially identical, or identical to the ball milling of SiO_(x)powder with graphite as described in U.S. Pat. No. 6,638,662, which isalso incorporated herein by reference. Additionally or alternatively,conductivity-enhanced SiOx can be produced for use in the firstprelithiation procedure 112 by way of another technique, such as thermalCVD by which carbon or a carbon based material is deposited on theSiO_(x) powder prior to its reaction with the lithium powder.

Reacting SiO_(x) and/or conductivity-enhanced SiO_(x) powder withstabilized lithium powder can be carried out using a temperaturecontrolled mixing/reaction device that applies a high shear stress in aninert gas atmosphere (e.g., an argon atmosphere, or an atmospherecontaining helium), and which provides effective dissipation of heatgenerated during the reaction. Such a reaction device can be a ballmill, for instance, a planetary ball mill such as that described in U.S.Pat. No. 7,776,473, having a thermally regulated or thermally conductivereaction container, vessel, or jar in which SiO_(x) and/orconductivity-enhanced SiO_(x) powder with stabilized lithium powder aremixed. Mixing/reaction device related parameters that can influence ordetermine the characteristics of the partially lithiated SSLC materialinclude the heat release, heat transfer, and shear stress during thereaction, and the characteristics of the partially lithiated SSLCmaterial can vary with charge, rotational speed, and/or milling time, ina manner readily understood by individuals having ordinary skill in theart.

When electrical conductivity-enhanced SiO_(x) is used in the firstprocess portion 110, the electrical conductivity enhancement can resultin the SiO_(x) having a significantly improved thermal conductivity(e.g., when the electrical conductivity-enhanced SiO_(x) includes or isSiO_(x) reacted or coated with graphite), which can aid heat dissipationand thermal regulation during ball milling, as further detailed below.

The first process portion 110 further includes subjecting the partiallylithiated SSLC material to the second prelithiation procedure 114, inwhich the partially lithiated SSLC material is compressed (e.g.,compressed into pellets or pelletized in a conventional manner, such asby way of conventional pelletizing equipment (i.e., a pelletizer) orpress, or direct compression tableting equipment) and immersed in alithium based electrolyte solution (e.g., a lithium salt basedelectrolyte solution, or an equivalent thereto) in order to complete thereaction of unreacted lithium and SiO_(x) in the partially lithiatedSSLC material, until all unreacted lithium disappears and an enhanceduniformity or uniform composition of lithium silicides is achieved inthe SSLC material by lithium diffusion. The partially lithiated SSLCmaterial can alternatively be immersed in another type of chemicalsolution, for instance, an ester, a carbonate, or a solvent used in Liion battery electrolyte solvent, in a manner understood by individualshaving ordinary skill in the relevant art.

As a result of the second prelithiation procedure 114, the SSLC materialexhibits much more uniform or uniform lithiation, for instance, over ashorter or greatly or significantly reduced time period (e.g., ascompared to ball milling alone), as well as an extent of prelithiationthat is greater, significantly greater, or much greater than the extentof prelithiation achieved by the teachings of U.S. Pat. No. 7,776,473.In multiple embodiments, the first process portion 110 (i.e., the firstprelithiation procedure 112 in combination with the second prelithiationprocedure 114) results in a substantially complete, essentiallycomplete, or complete lithiation of the SSLC material, which includeslithium silicide uniformly or generally uniformly distributed therein.

The second prelithiation procedure 114 further and possibly completelylithiates the SSLC material in a uniform or highly uniform manner, whichenables the SSLC to achieve maximum volumetric plastic deformation ofthe SSLC material such that most of the free Si nanoparticles in theSSLC form lithium silicide. If the second prelithiation procedure 114 isnot carried out, there is a chance that the SSLC material may expandfurther or greatly when the delithiathed SSLC material is charged duringactual use as anode active material, which will cause unwantedvolumetric expansion. Additionally, if the SSLC material is more fullyor completely liathiated by way of the second prelithiation procedure114, the energy density and capacity of the SSLC material can beenhanced or maximized/optimized such that the Si nano particles in theamorphous delithiated SSLC material have greater capacity to receivelithium ions without excessive increase in its volume. In variousembodiments, after the first process portion 110 (i.e., upon completionof the first and second prelithiation procedures 112, 114, the extent ofprelithiation of the SSLC material can range from approximately 25%-75%,or approximately 25%-100%.

Following the first process portion 110 (i.e., after the first andsecond prelithiation procedures 112, 114 have been performed), invarious embodiments the SSLC material production process 100 furtherincludes a second process portion 120 that involves delithiating theprelithiated SSLC material in a delithiation reactor, to thereby producea delithiated SSLC material in which amorphous and/or crystallitesilicon nanoparticles are embedded in an Si:LSC matrix, and anyunreacted lithium and active lithium silicide do not remain. The secondprocess portion 120 involves dispersing the lithiated SSLC material inan organic solvent or an organic solvent mixture, and controllablyreacting this dispersed lithiated SSLC material with an alcohol thatreacts with lithium silicide such that the lithiated SSLC material loseslithium, thereby becoming essentially completely, completely, or fullydelithiated SSLC material. For instance, after the second processportion 120, the delithiated SSLC material can have a lithium silicidecontent of less than approximately 0.5% by weight.

FIG. 2 is a schematic illustration of a representative delithiationreactor 200 in accordance with an embodiment of the present disclosure.In an embodiment, the delithiation reactor includes a reaction vessel210; an alcohol source or supply 212 having a conduit or feed line intothe reaction vessel 210; an inert gas supply (e.g., an argon gas supply)214 having a conduit or feed line into the reaction vessel 210; a gasexhaust 215 having a conduit or exhaust line leading from the reactionvessel 210; and a first temperature probe 216 having a temperaturesensing device (e.g., a thermocouple) disposed in the reaction vessel210. The reaction vessel 210 is disposed in a cooling bath 220, which isassociated with or includes a second temperature probe 226 having atemperature sensing device (e.g., a thermocouple) disposed therein.

FIGS. 3A-3C are illustrations showing representative microstructuralcharacteristics of SiO_(x) (x=1); representative microstructuralcharacteristics of prelithiated SSLC produced in accordance with anembodiment of the present disclosure; and representative microstructuralcharacteristics of delithiated SSLC produced in accordance with anembodiment of the present disclosure, respectively. In view of FIG. 1and FIGS. 3A-3C, the first process portion 110 reacts SiO_(x) powderwith lithium powder to irreversibly transform or plastically deform theSiO_(x) powder into significantly, substantially completely, orcompletely prelithiated SSLC material; after which the prelithiated SSLCmaterial is completely delithiated to produce a porous, plasticallydeformable Si:LSC matrix that carries amorphous and/or crystalline nanosilicon particles, which can be reversibly lithiated and delithiated, ina manner readily understood by individuals having ordinary skill in theart. Thus, when the delithiated SSLC material is used as a lithium ionbattery anode material, these nano silicon particles carried by theSi:LSC matrix can act as lithium intercalation sites (or analogously,lithium “receptor sites” and “donor sites,” respectively), during anodematerial lithiation and delithiation.

In the delithiated SSLC material produced in accordance with embodimentsof the present disclosure, the matrix of lithium silicate that carriesthe silicon nano particles behaves in a manner similar or analogous to asolid electrolyte that transports lithium ions (in)to the silicon nanoparticles, while greatly or dramatically reducing or minimizing volumechanges. This is achieved by tightly controlling the uniformdistribution of silicon nano particles and the porosity of the Si:LSCmatrix during the anode material manufacturing process.

With reference again to FIG. 1, the third process portion 130 involvesfiltering, washing, and possibly drying the delithiated SSLC material ina conventional manner, for instance, drying in air and possibly dryingunder negative pressure or vacuum, where such drying can occur at atemperature between 100-120° C. (e.g., in an oven)). In the fourthprocess portion 140, the delithiated SSLC material can be mechanicallystabilized or structurally reinforced by way of coating with one or moretypes of materials, such as one or more of LiAlO₃, Al₂O₃, TiO₂, AlF₃,and LiF in a conventional manner. Finally, in the fifth process portion150, the delithiated SSLC material or the mechanically stabilizeddelithiated SSLC material is treated, coated, or combined with one ormore carbon and/or carbon based materials such as graphite, carbonblack, graphene, buckyballs, carbon nanotubes, carbon megatubes, and/orcarbon nanobuds in a conventional manner. In several embodiments, thefifth process portion 150 involves coating the delithiated SSLC materialor the mechanically stabilized delithiated SSLC material with a carbonbased material (e.g., graphite) by way of CVD, which partially fuses thecarbon based material with the delithiated SSLC material.

Following the fifth process portion 150, the delithiated SSLC materialcan be used as a non-aqueous electrolyte secondary cell negativeelectrode (anode) material.

Further Aspects of a Representative SSLC Material Production Process

In view of the foregoing, a particulate delithiated SSLC material inaccordance with an embodiment of the present disclosure can be producedin powder form, which has a microstructure in which amorphous and/orcrystalline silicon on the atomic level is dispersed as nano silicongrains in the Si:LSC matrix thereof. The size of the nano silicon grainsis typically in the range of 0.5-80 nm, and the Si:LSC matrix typicallyexhibits a grain size of 10-200 nm. The SSLC material particles, i.e.,the SSLC powder particulates, typically have an average particle size of1 to 10 μm. In various embodiments, the delithiated SSLC material, i.e.,the SSLC material having no unreacted lithium or lithium silicidetherein, has a silicon content of 30 to 60% by weight, an oxygen contentof 25 to 40% by weight; and a lithium content of 10 to 20% by weight.

In multiple embodiments, the fully prelithiated SSLC material have acomposition of approximately 31% silicon by weight, approximately 32%lithium by weight, and approximately 35% oxygen by weight; and the fullydelithiated SSLC material can have a composition of approximately 37%silicon by weight, approximately 18% lithium by weight, andapproximately 43% oxygen by weight.

The delithiated SSLC material can be prepared by reacting silicon oxidepowder typically characterized as SiO_(x) (0.8<x<1.6) with metalliclithium powder at controlled temperature. In the absence of electricalconductivity enhancement, the SSLC material has a low electricalconductivity. Hence, it is recommended that the SiO_(x) and/or thesurface of the delithiated SSLC material undergo treatment or reactionwith carbon or carbon based materials to enhance their electricalconductivity. Carbon coatings can be easily formed by way of thermalCVD, such as thermal CVD of graphite, which improves conductivity to ahigh level. Additionally or alternatively, a highly conductive surfacecan be obtained by premilling SiO_(x) powder with an electronicallyconductive material such as graphite powder or carbon black powder. Theamount of carbon present in or coated on the SSLC powder is typically 3to 20% by weight, based on the weight of the SSLC material powder. Thecarbon coating layer maintains a chemical bond with the surface of theSSLC material, and can remain on the surface even after large volumeexpansion.

EXAMPLE 1

Silicon oxide powder (SiO_(x), 0.8<x<1.6, Sigma Aldrich) and/or siliconoxide based powder is milled with lithium powder in a high energy ballmilling machine using hexane as a dispersing medium under a protectiveargon atmosphere. The silicon oxide and/or silicon oxide based powder ispremixed with stabilized lithium powder SLMP® (FMC Corporation) under aninert gas (argon) atmosphere in a closed container or vial, in 5, 10,15, and 20% by weight increments (e.g., 6 g SiOx is premixed with 3.8 gSLMP® to prepare a sample having approximately 6 g SiOx and 0.6 glithium, or an approximate 10% by weight sample, in a manner readilyunderstood by individuals having ordinary skill in the relevant art.While metallic lithium is generally available in powder, foil or massform, the use of stabilized lithium powder SLMP® (FMC Corporation) istypically preferable.

The silicon oxide and/or silicon oxide-based material premixed withmetallic lithium is transferred into a ball milling container, vessel,or jar (e.g., a 50 ml or larger container); and then ball milled, i.e.,mechanically mixed for reaction with lithium in a ball milling machinehaving an effective heat dissipation capability. The reaction containeris be tightly sealed with rubber rings under an inert gas atmospheredesigned for cooling control, and capable of mixing under high shearstresses. A planetary high energy ball milling machine is a good exampleball milling machine for such milling process. For instance, a planetaryball milling machine produced by Retsch GmbH, containing a predeterminednumber of milling stainless steel or zirconium oxide balls, can be used.The mill has a tight closure, potential heat dissipation of balls, andhigh shear stress. The temperature of the reaction container iscontrolled in the range of 40 to 150° C.

In a representative embodiment, the ball milling container is rotated inforward and backward directions each for ten minutes while maintainingan internal controlled temperature (e.g., 40-150° C.). After ballmilling, the container is allowed to cool, e.g., to room temperature,after which the partially prelithiated silicon-silicon oxide-lithiumcomposite (i.e., the partially lithiated SSLC material) is removed fromthe container. In order to enhance or maximize the extent and uniformityof prelithiation, this partially prelithiated SSLC material issubsequently compressed into pellets in a conventional manner, withhexane elimination by filtration or evaporation. The pellets are thenplaced in a vessel or container and immersed in an electrolyte or amixture of electrolytes in order to complete the reaction of unreactedlithium with SiO_(x) powder, to thereby produce the further,substantially completely, or completely prelithiated SSLC material,which exhibits enhanced uniformity or uniform prelithiation. Thetemperature is controlled to prevent violent reaction of unreactedlithium with SiO_(x).

More particularly, in a solid state reaction between a solid siliceousmaterial such as SiO_(x) powder and metallic lithium, the rate oflithium diffusion into the solid siliceous material is generally low. Itis difficult for metallic lithium to react uniformly with the solidSiO_(x) powder, and as a result, various chemical compositions such asunreacted lithium, unreacted SiO₂, and various kinds of lithium silicideand lithium silicates can be produced. One effective approach forcomplementing this lithium shortage is to compress the prelithiatedpowder into pellets and immerse the compressed pellets in an electrolyteor a mixture of electrolytes. In order to avoid a violent reaction, thetemperature is controlled to start from a temperature between 5° C. toroom temperature.

The pellets of the enhanced, substantially completely, or completely anduniformly prelithiated SSLC material are subsequently ground in a mortarafter filtration, and dispersed in hexane again. To this newly preparedslurry, ethanol is slowly added. Lithium silicide reacts with theethanol, and the prelithiated SSLC material thereby loses lithium.Alcohol is added until bubble formation is stopped, indicating that thecompletely delithiated SSLC material has been produced. After filtrationand washing, the powder can be coated with LiAlO₃, Al₂O₃, TiO₂, AlF₃,LiF, and/or other material(s) (e.g., at a coating thickness ofapproximately 20-50 nm, or about 30 nm) for mechanical stabilization,and/or dried and coated with carbon (e.g., graphite) by way of CVD.

The silicon oxide (SiO_(x), 0.8<x<1.6) and/or silicon oxide-basedmaterial is milled through high energy ball milling until it reaches apredetermined or desired size distribution. Consequently, it reacts withmetallic lithium powder by way of the ball milling process in the inertgas atmosphere. Because the reaction is strongly exothermic, it caneasily ignite and lead to a significant particle growth of Si and SiO₂and loss of electrochemical activity upon disproportionation. To controlthe growth of the unreacted SiO₂ phase, the temperature of the reactioncontainer should be controlled below 150° C.

SiO_(x)(x≅1) is a mixture of Si and SiO₂ at the nano scale. Because thevolume of crystalline Si therein is 33%, SiO_(x) has a structure inwhich nano crystalline Si particles are embedded in the matrix of SiO₂.

When 2SiO₂ reacts with (4+y)Li, it forms an Li_(y)Si:Li₄Si:O₄ composite,as follows:4SiO+(4+3y)Li→2Li_(y)Si+Li_(y)Si:Li₄SiO₄ during lithiation  (5)

where the Li_(y)Si is in the form of nano particles, and theLi_(y)Si:Li₄SiO₄ is in the form of a matrix that carries the Li_(y)Sinano particles. When delithiation occurs,2Li_(y)Si+Li_(y)Si:Li₄SiO₄→2Si+Si:Li₄SiO₄ during de-lithiation  (6)where the Si is in the form of nano particles, and the Si:Li₄SiO₄ is inthe form of a matrix that carries the Si nano particles.

During lithiation/de-lithiation, Li_(y)Si:Li₄SiO₄ and Si:Li₄SiO₄ canexist as a matrix at a certain level of lithiation (e.g., up to a limitof approximately 50%). If the reaction processes to an ignited state,the lithium silicide (Li_(y)Si) from the matrix can be agglomerated intothe nano lithium silicide particles. As a result, lithium silicideparticles can grow, and the lithium silicide becomes part of the matrixas the matrix of Li_(y)Si:Li₄SiO₄ loses lithium silicide to the lithiumsilicide particles. This will cause a large volume change duringlithiation and delithiation and deteriorate cyclic performance.Therefore, it is important to perform the reaction of lithium withSiO_(x) at a temperature not exceeding 150° C.

The use of SiO_(x) that has been pretreated or precoated with a materialthat enhances its thermal conductivity prior to ball milling with SLMP®can improve heat dissipation and temperature control within the ballmilling container during ball milling. For instance, the SiO_(x) can bepretreated or precoated with a carbon or carbon based material such asgraphite (e.g., by way of ball milling and/or CVD, as set forth above),which concurrently increases the electrical conductivity and the thermalconductivity of the SiO_(x). Furthermore, because of the improved heatdissipation and better temperature control, a larger amount of lithiumpowder can be ball milled with a given amount of suchpretreated/precoated SiO_(x) without deleterious effect of uncontrolledheating and SiO powder agglomeration. For instance, instead of 10%incremental addition of SLMP, approximately 25% incremental addition ofSLMP® can occur when the SiO_(x) is pretreated or precoated with acarbon or carbon based material such as graphite.

During lithiation of SiO_(x) anodes, the volume increase of Li_(y)Siphase plastically deforms the Li₄SiO₄ phase in the matrix ofLi_(y)Si:Li₄SiO₄. Because the volume ratio of Li_(4.4)Si to Li₄SiO₄ inthe matrix is 1, the Li₄SiO₄ phase may not exist as a matrix when y isclose to 4.4. During delithiation, Li_(y)Si loses lithium and its volumerapidly decreases. However, the plastically deformed L₄SiO₄ remainssubstantially or essentially unchanged or stays the same at a certainlevel, and becomes very porous. This can explain how the volume changebefore and after de-lithiation is minimized by the plastic deformationof the Li₄SiO₄ phase. Reaction (4) above indicates that 2Li_(y)Si nanoparticles are embedded in the matrix of Li_(y)Si:Li₄SiO₄. As y is closeto 4.4, the volume ratio of 2Li_(y)Si to Li_(y)Si:Li₄SiO₄ is 1, and thevolume increase of 2Li_(y)Si also contributes to the large plasticdeformation of the Li_(y)Si:Li₄SiO₄ phase and leaves larger permanentdefects in the matrix. This mechanism indicates that the volume changeof lithiated SiO_(x) anodes can be significantly minimized duringlithiation/de-lithiation. As a result, the micro-sized SiO_(x) anodegenerally shows much better cyclic performance than micro-sized siliconanode when both are well coated with conducting carbon.

The plastically deformed Li_(y)Si:Li₄SiO₄ may be fragile and maycollapse as a result of lithiation/delithiation cycling across manycycles. In order to enhance the mechanical property of the matrix duringcycling, nano film(s) such as LiAlO₂, Al₂O₃, TiO2, AlF₃, LiF, SiO₂and/or one or more other kinds of metal oxide can coat the SiO_(x) anodeafter delithiation of Li_(y)Si. The coating layer can fill the defectson the surface of SiO_(x) anodes and support their mechanical stability.Moreover, the coating layer can aid the formation and possibly enhancethe stability of a solid electrode interphase (SEI) layer formed at theanode-electrolyte interface in a lithium ion battery cell. Stillfurther, the coating layer can increase the likelihood that a Li ionbattery cell anode made using delithiated SSLC material in accordancewith an embodiment of the present disclosure remains sufficientlyelectrically conductive across many charging/discharging orlithiation/delithiation cycles (or correspondingly,expansion/contraction cycles) over time.

To improve or further improve the conductivity of the delithiated SSLCmaterial, carbon and/or carbon based material(s) can be applied to thedelithiated SSLC material particles by thermal CVD, specifically byheating a CVD chamber in which the delithiated SSLC material resides toa temperature of 600 to 900° C. and feeding an organic matter gas orvapor into the CVD chamber. The conductive carbon can be insufficientlyfused on the surface of the composite particles below 800° C. However,above a certain temperature, crystalline Si particles embedded in thematrix of SiO₂ in SiO_(x) structure can be agglomerated with the siliconphase from the Si:Li₄SiO₄ matrix and then the crystalline silicon cangrow. This increases the volume of silicon particles larger than thevolume of Li₄SiO₄ and destroys the nano Si particles embedded Li₄SiO₄structure and finally deteriorates the cyclic performance. As a result,the CVD chamber temperature should remain in the range of 800 to 950° C.

The organic material used to coat carbon via CVD can be selected frommaterials capable of forming carbon (graphite) through pyrolysis at theabove temperature range under an inert atmosphere. Examples ofhydrocarbons that can form such carbon include but are not limited tomethane, ethane, ethylene, acetylene, propane, butane, butene, pentane,isobutane, and hexane alone or in an admixture thereof; and monocyclicto tricyclic aromatic hydrocarbons such as benzene, toluene, xylene,styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol,nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene,and phenanthrene alone or in an admixture thereof. Organic polymers orpolymeric or oligomeric siloxanes having large hydrocarbon side chainscan alternatively be used as a carbon source.

The delithiated SSLC material powder can be used as a negative electrodematerial in order to construct a non-aqueous electrolyte secondary cell,especially a lithium ion secondary cell, having a high capacity, goodcycle performance and low irreversible capacity from the first cycle.The positive electrode active material can be selected from commerciallyavailable cathodes such as LiCoO₂, lithium nickel cobalt manganese oxide(NCM), lithium rich NCM, lithium nickel cobalt oxide doped withaluminum, and spinel lithium manganese oxide. The electrolytes usedherein can be lithium salts such as one or more of lithium perchlorate,LiPF₆, LiBF₆, and LITFSI (Lithium Bis(Trifluoromethanesulfonyl)Imide) innon-aqueous solution form. Examples of the non-aqueous solvents includepropylene carbonate, ethylene carbonate, dimethoxyethane,.gamma.-butyrolactone and 2-methyltetrahydrofuran, alone or in anadmixture.

EXAMPLE 2

A second Example is described hereafter, which is performed in a manneranalogous or substantially identical to that described above for Example1, in a manner readily understood by individuals having ordinary skillin the relevant art in view of the description herein.

SiO_(x) powder (SiO_(x), 0.8<x<1.6, Sigma Aldrich) is ball milled for upto 5 hours in an ethanol solvent. After SiOx particle size reduction to˜6 um occurs, the ethanol is evaporated, and graphite powder such asMage3 graphite powder having an average particle size (D50) of 23 μm(Hitachi Chemical Co. Ltd., Tokyo, Japan) is added. The SiO_(x)particles and graphite powder are ball milled an additional 2 hours,thus producing a SiO_(x) based powder, namely, SiOx/graphite powderintended for prelithiation in accordance with an embodiment of thepresent disclosure. Next, SLMP® powder (FMC Corporation) is added to theball mill container, and ball milling for an additional 30 minutes leadsto the partial prelithiation of the original SiOx/graphite powder, andthe production of a partially prelithiated SSLC material. The partiallyprelithiated SiOx/graphite powder is next compressed into pellets in aconventional manner, with hexane elimination by filtration orevaporation. The pellets are then immersed in an electrolyte or amixture of electrolytes in a vessel or container in order to completethe reaction of unreacted lithium with SiO_(x) powder, to therebyproduce the enhanced, substantially completely, or completelyprelithiated SSLC material having a uniform, essentially uniform, orsubstantially uniform distribution of lithium silicides therein.

Delithiation occurred in the delithiation reactor 200 in the manner setforth above to produce the completely delithiated SSLC material powder.The ethanol/powder slurry is dried initially using a centrifuge,followed by ambient air flow. Dried delithiated SSLC material powder ismixed with carbon black and a binder in NMP solvent, and cast on Cufoil, with subsequent drying in a vacuum oven at 250° C., for use as anegative electrode for a Li ion battery.

Aspects of particular embodiments of the present disclosure address atleast one aspect, problem, limitation, and/or disadvantage associatedwith existing SiO_(x) based anode materials, compositions, orstructures; processes for the preparation of SiO_(x) anode materials,compositions, or structures; and SiO_(x) based anodes. While features,aspects, and/or advantages associated with certain embodiments have beendescribed in the present disclosure, other embodiments may also exhibitsuch features, aspects, and/or advantages, and not all embodiments neednecessarily exhibit such features, aspects, and/or advantages to fallwithin the scope of the present disclosure and the claims includedherewith. It will be appreciated by a person of ordinary skill in theart that several of the above-disclosed systems, components, processes,or alternatives thereof, may be desirably combined into other differentsystems, components, processes, and/or applications. In addition, aperson of ordinary skill in the relevant art can make variousmodifications, alterations, and/or improvements to various embodimentsdisclosed herein, which remain within the scope of the presentdisclosure and the claims.

The invention claimed is:
 1. A method for producing a silicon:siliconoxide: lithium composite (SSLC) material, comprising: performing aprelithiation process to produce a prelithiated SSLC material, theprelithiation process comprising: producing a partially lithiated SSLCmaterial by way of a mechanical mixing procedure comprising millingsilicon oxide powder and lithium powder; and producing a furtherprelithiated SSLC material by way of a spontaneous lithiation procedurecomprising: compressing the partially lithiated SSLC material matrixmaterial; and exposing the compressed partially lithiated SSLC materialto a lithium based electrolyte, wherein spontaneous lithiation procedurecompletes reaction of unreacted lithium and SiO_(x) in the partiallylithiated SSLC material, until unreacted lithium disappears and auniform composition of lithium silicides is achieved in the SSLCmaterial by lithium diffusion; performing a delithiation processfollowing the prelithiation process to produce a delithiated SSLCmaterial, the delithiation process comprising: dispersing the compressedfurther prelithiated SSLC material in a liquid carrier medium to therebyproduce a dispersed prelithiated SSLC material; and exposing thedispersed prelithiated SSLC material to a volume of one or more organicsolvents to thereby react lithium silicide within the dispersedprelithiated SSLC material with the one or more organic solvents andextract lithium from the dispersed prelithiated SSLC material, untilreactivity of lithium silicide within the dispersed prelithiated SSLCmaterial with the one or more organic solvents ceases, wherein thevolume of the one or more organic solvents acts as a reservoir withrespect to reacting with lithium silicide within the dispersedprelithiated SSLC material, wherein the delithiated SSLC materialcomprises a porous plastically deformable Si:lithium silicate composite(Si:LSC) matrix having nano silicon particles embedded therein.
 2. Themethod claim 1, wherein the delithiated SSLC material exhibits a lithiumsilicide content of less than 0.5% by weight.
 3. The method of claim 1or 2, wherein the delithiated SSLC material has a particle size of 1-10μm, the Si:LSC matrix exhibits a grain size of 10-200 nm, and the nanosilicon particles have a particle size of 5-80 nm.
 4. The method ofclaim 1, wherein the delithiated SSLC material has a silicon content of30%-60% by weight, an oxygen content of 25%-40% by weight, and a lithiumcontent of 10%-20% by weight.
 5. The method of claim 1, wherein thedelithiated SSLC material has a composition of approximately 37% siliconby weight, approximately 18% lithium by weight, and approximately 43%oxygen by weight.
 6. The method of claim 1, wherein the liquid carriermedium comprises an aprotic solvent, and the one or more organicsolvents comprise an alcohol.
 7. The method of claim 1, wherein theliquid carrier medium comprises hexane, and the one or more organicsolvents comprise ethanol, glycerol, and/or polyvinyl alcohol (PVA). 8.The method of claim 1, wherein the silicon oxide powder is characterizedas SiOx (0.8<x<1.6), wherein the mechanical mixing procedure comprisesball milling the silicon oxide powder with the lithium powder, andwherein the lithium powder comprises SLMP®.
 9. The method of claim 1,further comprising performing a first electrical conductivityenhancement process prior to the prelithiation process, wherein thefirst electrical conductivity enhancement process comprises least one ofball milling the silicon oxide powder with a carbon based material, andcoating the silicon oxide powder with a carbon based material.
 10. Themethod of claim 1, further comprising performing a second electricalconductivity enhancement process after the delithiation process, whereinthe second electrical conductivity enhancement process comprises atleast one of ball milling the silicon oxide powder with a carbon basedmaterial, and coating the silicon oxide powder with a carbon basedmaterial.
 11. The method of claim 9, wherein the carbon based materialcomprises at least one of graphite, carbon black, buckyballs, carbonnanotubes, carbon megatubes, and carbon nanobuds.